更新:该错误从SQL Server 2008返回为SqlException错误。我遇到错误的地方似乎是单线程的。但可能由于同时运行多个测试(VS2008sp1中的MSTest),我会遇到单元测试交互而出现错误。但失败的测试看起来像:
- 创建一个对象并将其保存在DB事务内(提交)
- 创建TransactionScope
- 尝试打开连接-在这里我得到了具有此类堆栈跟踪的SqlException:
.
System.Data.SqlClient.SqlException: Transaction context in use by another session.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.TdsExecuteTransactionManagerRequest(Byte[] buffer, TransactionManagerRequestType request, String transactionName, TransactionManagerIsolationLevel isoLevel, Int32 timeout, SqlInternalTransaction transaction, TdsParserStateObject stateObj, Boolean isDelegateControlRequest)
at System.Data.SqlClient.SqlInternalConnectionTds.PropagateTransactionCookie(Byte[] cookie)
at System.Data.SqlClient.SqlInternalConnection.EnlistNonNull(Transaction tx)
at System.Data.SqlClient.SqlInternalConnection.Enlist(Transaction tx)
at System.Data.SqlClient.SqlInternalConnectionTds.Activate(Transaction transaction)
at System.Data.ProviderBase.DbConnectionInternal.ActivateConnection(Transaction transaction)
at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()
我找到了这些帖子:
- http://blogs.msdn.com/asiatech/archive/2009/08/10/system-transaction-may-fail-in-multiple-thread-environment.aspx
- http://msdn.microsoft.com/en-us/library/ff649002.aspx
但是我不明白 "多个线程在事务范围内共享同一个事务将导致以下异常:'Transaction context in use by another session.'" 是什么意思。所有单词我都懂,但是不理解它的意义。
实际上,我可以在线程之间共享系统事务。甚至还有专门的机制 - DependentTransaction类和Transaction.DependentClone方法。
我正在尝试复现第一个帖子中的一个用例:
- 主线程创建DTC事务,接收DependentTransaction(在主线程上使用Transaction.Current.DependentClone创建)
- 子线程1通过基于依赖事务创建的事务范围(通过构造函数传递)注册在此DTC事务中
- 子线程1打开连接
- 子线程2通过基于依赖事务创建的事务范围(通过构造函数传递)注册在此DTC事务中
- 子线程2打开连接
代码如下:
using System;
using System.Threading;
using System.Transactions;
using System.Data;
using System.Data.SqlClient;
public class Program
{
private static string ConnectionString = "Initial Catalog=DB;Data Source=.;User ID=user;PWD=pwd;";
public static void Main()
{
int MAX = 100;
for(int i =0; i< MAX;i++)
{
using(var ctx = new TransactionScope())
{
var tx = Transaction.Current;
// make the transaction distributed
using (SqlConnection con1 = new SqlConnection(ConnectionString))
using (SqlConnection con2 = new SqlConnection(ConnectionString))
{
con1.Open();
con2.Open();
}
showSysTranStatus();
DependentTransaction dtx = Transaction.Current.DependentClone(DependentCloneOption.BlockCommitUntilComplete);
Thread t1 = new Thread(o => workCallback(dtx));
Thread t2 = new Thread(o => workCallback(dtx));
t1.Start();
t2.Start();
t1.Join();
t2.Join();
ctx.Complete();
}
trace("root transaction completes");
}
}
private static void workCallback(DependentTransaction dtx)
{
using(var txScope1 = new TransactionScope(dtx))
{
using (SqlConnection con2 = new SqlConnection(ConnectionString))
{
con2.Open();
trace("connection opened");
showDbTranStatus(con2);
}
txScope1.Complete();
}
trace("dependant tran completes");
}
private static void trace(string msg)
{
Console.WriteLine(Thread.CurrentThread.ManagedThreadId + " : " + msg);
}
private static void showSysTranStatus()
{
string msg;
if (Transaction.Current != null)
msg = Transaction.Current.TransactionInformation.DistributedIdentifier.ToString();
else
msg = "no sys tran";
trace( msg );
}
private static void showDbTranStatus(SqlConnection con)
{
var cmd = con.CreateCommand();
cmd.CommandText = "SELECT 1";
var c = cmd.ExecuteScalar();
trace("@@TRANCOUNT = " + c);
}
}
在完成根TransactionScope的调用中失败。但错误不同:Unhandled Exception: System.Transactions.TransactionInDoubtException: 事务存在疑问。---> 已过期。在操作完成之前已超时或服务器没有响应。
总之,我想了解“事务上下文正在被另一个会话使用”的含义以及如何重现它。